Nano

Molecule-based devices may govern the advancement of the next generation's logic and memory devices. Molecules have the potential to be unmatched device elements as chemists can mass produce an endless variety of molecules with novel optical, magnetic and charge transport characteristics. However, the biggest challenge is to connect two metal leads to a target molecule(s) and develop a robust and versatile device fabrication technology that can be adopted for commercial scale mass production. This paper discusses distinct advantages of utilizing commercially successful tunnel junctions as a vehicle for developing molecular spintronics devices. We describe the use of a prefabricated tunnel junction with the exposed sides as a testbed for molecular device fabrication. On the exposed sides of a tunnel junction molecules are bridged across an insulator by chemically bonding with the two metal electrodes; sequential growth of metal–insulator–metal layers ensures that separation between two metal electrodes is controlled by the insulator thickness to the molecular device length scale. This paper highlights various attributes of tunnel junction-based molecular devices with ferromagnetic electrodes for making molecular spintronics devices. We strongly emphasize a need for close collaboration between chemists and magnetic tunnel junction (MTJ) researchers. Such partnerships will have a strong potential to develop tunnel junction-based molecular devices for futuristic areas such as memory devices, magnetic metamaterials, high sensitivity multi-chemical biosensors, etc.

Gold-coated superparamagnetic iron oxide nanoparticles (SPIONs) coated with methyl-polyethylene glycol (mPEG) are synthesized and investigated as a magnetic resonance (MR) imaging contrast agent. The synthesized mPEG-core@shells are characterized by UV-visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), vibrating sample magnetometry (VSM), zeta-potential analysis and X-ray diffraction (XRD). In addition, the transverse relaxivity of the mPEG-core@shells is measured using a 3 T MRI scanner. The cytotoxicity of the mPEG-core@shells is tested in the LNCaP cell line using an 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results show that the mPEG-core@shell particles are semispherical with hydrodynamic size of ∼ 65 nm and a transverse relaxivity of 162.3 mM^-1 S^-1. The mPEG-core@shell particles demonstrate good stability in biological media without any significant in vitro cytotoxicity under high cellular uptake conditions. Finally, in vivo imaging shows that mPEG-core@shells are a potential contrast agent for use in early-stage detection.

We present the effect of post-implantation annealing conditions on the structural and optical quality of InAs quantum dots (QDs) grown by combination of focused ion beam (FIB) and molecular beam epitaxy (MBE) approach. A FIB of Ga⁺ ion was employed to pattern a homogeneously GaAs buffer layers and then, an in situ annealing step followed by InAs deposition was performed. Three different post-implantation annealing conditions were tested and under well-optimized conditions, a dislocation and defect-free InAs QDs growth on FIB patterned surface was successfully achieved. Furthermore, using photoluminescence (PL) study, we demonstrate that our best sample shows almost similar optical quality as MBE grown QDs on unimplanted GaAs surface. The patterning technique described here can presumably be applied to systems other than InAs/GaAs and highly interesting for site-controlled nucleation of QDs that finds its potential applications in nanooptoelectronic devices.

Mn-FeO_x/carbon nanotubes (CNTs) catalysts were firstly prepared via simple incipient wetness method and used for low-temperature selective catalytic reduction (SCR) of NO with NH₃. The structure and surface properties of the catalysts were characterized by N₂ sorption, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction by hydrogen (H₂-TPR). It was found that Mn-FeO_x/CNTs catalyst exhibited excellent low-temperature SCR activity and SO₂ resistance. XRD patterns revealed that metal oxides catalysts were possessed of amorphous structure. FESEM and TEM images showed that metal oxides catalysts were successfully supported on CNTs. The XPS results indicated that the obtained catalyst presented high Mn⁴⁺/Mn³⁺ and O_S/(O_S + O_L) ratios. The H₂-TPR profiles showed that Mn-FeO_x/CNTs catalyst possessed better low-temperature reducibility. Besides, the obtained catalyst exhibited better SO₂ resistance.

In this paper, it is described that the motion of water droplets on the hydrophobic surface of ZnO nanorod array impregnated lubricant, is called slippery liquid-infused porous surface (SLIPS). The energy gradient required to induce the motion of the droplets is created on the boundary of superhydrophobic ZnO nanorod array and SLIPS. Because of the lower viscous force of SLIPS, the water droplet can rapidly move for longer distance on the surface. In view of changing the release distance of water droplet, the mechanism for the rapid movement is discussed. The results indicate that the movement distance of water droplet markedly increases with the increasing of the release distance. Because the potential energy of the height is converted into kinetic energy, the water droplet intensively collides the interface between ZnO nanorod array and SLIPS. This impact makes the water droplet distort, which enhances the driving force. These new findings will not only deepen our understanding of the relationship between surface structure and dynamic wetting properties, but also afford the new notion and beneficial reference for designing liquid droplet transportation devices in micro-fluidic systems.

Objective: A major limitation in gene delivery applications employing nanocarriers is the inflammatory response elicited when administered in vivo. The mode of complexation of the oligonucleotide with the carrier can alter its interactions with biomolecules, a fact that has not been explored for lipoplexes hitherto. Materials: Liposomes prepared by thin film hydration were used to form lipoplexes of si-RNA and DNA, which exhibited a smaller size and a shift toward negative zeta potential when compared with blank liposomes. Results: The oligonucleotides wrap over the liposome surface and the surface coverage depends on the number of base pairs. The colloidal stability, protein resistance and cell uptake of lipoplexes were found to be dependent on surface charge and PEG. The lipoplexes with si-RNA did not induce cytokine production in BALB/c mice. Conclusion: The results highlight the importance of PEGylation for achieving good protein resistance without compromising cell uptake and therapeutic efficiency.

In this work, the nonlinear refractive properties of graphene suspension at different concentration levels are investigated by means of Z-scan technique with continuous wave low power laser beams at 532 nm and 635 nm. Results show that the dispersion of graphene in water exhibits negative nonlinear refractive index in continuous wave regime, which is mainly attributed to thermal nonlinear effect. We find that the absorption coefficient and nonlinear refractive index of the samples increase with increasing the concentration level of the graphene. Moreover, it is obtained that the nonlinear refractive index of the samples at different concentration levels depends on the wavelength of laser beam.

In this work, the sulfonated reduced graphene oxide (SRGO) was synthesized and proposed as an enhanced anode material for lithium ion battery (LIB). The result shows that the SRGO has an improved battery performance (i.e., ∼341.7 mAh/g and ∼190.6 mAh/g corresponds to SRGO and RGO at the 100th cycle with a current density of 200 mA/g) and superior cycling stability compared with pristine reduced graphene oxide (RGO). These are attributed to the improved specific surface area (448.35 m²/g) and conductivity (2.5 × 10^-4 S/m). Further, the SRGO exhibits good rate capability and excellent energy density at various current densities ranging from 50 mAh/g to 2000 mAh/g, suggesting that SRGO could be a promising anode material for high capacity LIB.

A two-step method for the preparation of hybrid materials consisting of multi-walled carbon nanotubes (MWCNTs) attached to graphene nanoplatelets (GNPs) was proposed. Firstly, poly (acryloyl chloride) was grafted in situ onto the surface of MWCNTs. Secondly, the obtained MWCNTs (MWCNTs-PACl) were reacted with acid-treated GNPs to form a nanotube–polymer–graphene hybrid. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA) were used to investigate the forming of the hybrid materials. FTIR results showed that MWCNTs/PACl and GNPs were successfully bridged by chemical bonds like O–C = O and C–O–C. Raman spectroscopy furthermore revealed that acryloyl chloride can be used to connect the MWCNTs and GNPs due to the defects of MWCNTs, and consequently the defects of the hybrid materials were limited. Meanwhile, TEM observation demonstrated the nanostructure clearly in which the MWCNTs with a polymer layer were attached successfully on the surface of GNPs. And TGA curves reflected that the content of MWCNTs and GNPs was about 46.5% in the hybrid materials. In addition, the tensile tests results showed that MWCNTs/GNPs hybrid materials can improve the mechanical performance of epoxy composites in higher degree, compared with MWCNTs or GNPs particles alone.

Molecule-based spintronics devices (MSDs) are highly promising candidates for discovering advanced logic and memory computer units. An advanced MSD will require the placement of paramagnetic molecules between the two ferromagnetic (FM) electrodes. Due to extreme fabrication challenges, only a couple of experimental studies could be performed to understand the effect of magnetic molecules on the overall magnetic and transport properties of MSDs. To date, theoretical studies mainly focused on charge and spin transport aspects of MSDs; there is a dearth of knowledge about the effect of magnetic molecules on the magnetic properties of MSDs. This paper investigates the effect of magnetic molecules, with a net spin, on the magnetic properties of 2D MSDs via Monte Carlo (MC) simulations. Our MC simulations encompass a wide range of MSDs that can be realized by establishing different kinds of magnetic interactions between molecules and FM electrodes at different temperatures. The MC simulations show that ambient thermal energy strongly influenced the molecular coupling effect on the MSD. We studied the nature and strength of molecule couplings (FM and antiferromagnetic) with the two electrodes on the magnetization, specific heat and magnetic susceptibility of MSDs. For the case when the nature of molecule interaction was FM with one electrode and antiferromagnetic with another electrode the overall magnetization shifted toward zero. In this case, the effect of molecules was also a strong function of the nature and strength of direct coupling between FM electrodes. In the case when molecules make opposite magnetic couplings with the two FM electrodes, the MSD model used for MC studies resembled with the magnetic tunnel junction based MSD. The experimental magnetic studies on these devices are in agreement with our theoretical MC simulations results. Our MC simulations will enable the fundamental understanding and designing of a wide range of novel spintronics devices utilizing a variety of molecules, nanoclusters and quantum dots as the device elements.

A synergistic combination of properties between graphene oxide (GO) nanosheets and porphyrin molecules has been accomplished via the entrapment of the latter species within the pore space formed by parallel plates of the carbon material. A hybrid material, synthesized in this manner, would likely lead to the development of efficient photovoltaic cells, given the high capacity of porphyrin molecules to absorb sunlight or radiation of wavelength shorter than 700 nm as well as because of the excellent electron conduction and fine solar energy capture that can be achieved by the graphene substrate. Herein, materials consisting of trapped porphyrin molecules in-between GO plates have been prepared to develop preliminary solar cell devices for an efficient capture of sunlight energy. The hybrid systems created this way can be physicochemically characterized through diverse techniques, which include fluorescence emission to confirm and avail both the presence and manifest luminescent characteristics of the tetrapyrrolic species that are captured and retained in-between GO plates.

In this investigation, the effects of carbon nanotube (CNT) shape and distribution on nanocomposite failure are investigated. To achieve our goals, nanocomposites consisting of straight and sinusoidal CNTs with uniform and nonuniform distributions have been modeled. Failure of these nanocomposites is investigated using finite element simulations and micromechanics models. Initially, straight CNT-reinforced polymer is simulated and the stress–strain diagram for this nanocomposite is obtained. To validate our models, the simulation results of this nanocomposite are compared with those found in the literature. Then, sinusoidal CNT-reinforced polymers with uniform and nonuniform CNT distributions are modeled. The results are compared to determine the influence of CNT shape and distribution on nanocomposite failure mechanisms.

We report the synthesis of TiO₂-supported monometallic Ag, Sn and bimetallic AgSn nanoparticle catalysts prepared using sol–gel method via a rational nanoparticle encapsulation route. The samples were thoroughly characterized by ultraviolet-visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) with image mapping and Brunauer–Emmett–Teller (BET) surface area analyzer. The supported bimetallic AgSn catalyst had the anatase structure, surface area of 50 m²/g and 2.6 ± 0.6 nm particle size. The efficiency of the catalysts was evaluated on photodegradation of methylene blue (MB) dye under visible light. The photocatalytic activity of MB was significantly enhanced in the presence of bimetallic AgSn nanoparticles (NPs) as compared to individual metal nanoparticles. Reusability study of the photocatalyst showed that the catalyst can be reused upto 5 runs with minimal loss in activity. Kinetic study revealed that the degradation reaction follows a pseudo first-order pathway.

An ultrasensitive electrochemical immunosensor based on Nb-doped titanium dioxide was developed for detection of carcinoembryonic antigen (CEA). The electrochemical signal enhancement was due to the synergistic effect by NbT and nanogold. The influence factors (pH, temperature and incubation time) were investigated in detail. Under optimal conditions, the immunosensor was able to detect the concentration of CEA in the range of 0.5 ng ⋅ mL^-1 to 150 ng ⋅ mL^-1, with a lower detection limit of 8.95 pg ⋅ mL^-1. The proposed immunosensor showed high sensitivity, excellent selectivity and good stability.

Unlike synthesis of nanowires (1D nano-objects) the synthesis of nanoplatelets (2D nano-objects) has not been performed frequently. Herein, we report on the synthesis of Cu–Ge based on nanoplatelets with a high surface-to-volume ratio prepared by low pressure chemical vapor deposition (LPCVD) of Ge₂Me₆ and a mixture of Ge₂Me₆/PbEt₄. Nanostructured deposits are composed of Cu_1-xGe_x nanoplatelets, Ge nanowires and Ge nanoparticles. The nanoplatelets, which have the lateral size up to several tens of micrometers and thickness of 100–400 nm, belong to the cubic α phase of Cu₉₁Ge₉ alloy (Ge admixture in cubic Cu) and hexagonal ζ phase of Cu₈₅Ge₁₅ alloy. Nanowires composed of cubic Ge have a diameter of about 30 nm and length of several tens of micrometers. Lead does not enter any of these phases due to Pb–Cu and Pb–Ge immiscibility; therefore, it was observed as separate nanoparticles.

A major challenge in cancer therapy is destroying cancer cells with least side effects on healthy cells. In this paper, autonomous drug-encapsulated nanoparticle (ADENP) with a real feedback control is recommended to prevent from the growth of cancerous tumors and treatment of them. The proposed ADENPs, swarmly perform local drug delivery which leads to significant reduction in side effects on healthy tissues in comparison to global drug delivery. The proposed ADENPs every moment, take feedback directly from drugs and cancer cells and at any time decide how much drugs to release. Also, these ADENPs have the capability of distinguishing unhealthy from healthy tissues, and medication use of these nanoparticles is more efficient than drug carriers. Another feature of these ADENPs is their simple structure in comparison to nanorobots. Simulation results show that ADENPs successfully reduce the number of cancer cells with minimal side effects.